This invention relates generally to gas turbine engines and, more specifically, to measuring a bearing thrust load on gas turbine engine bearing assemblies.
At least some known gas turbine engines include rotating compressors and turbines. The rotating compressors and turbines are supported within a case by bearing assemblies. During operation, thrust loads may be induced to the bearing assemblies that damage and/or reduce an operational life of such bearing assemblies. Accordingly, bearing thrust forces are sometimes monitored to determine if such forces are high enough to damage and/or reduce the operational life of such bearing assemblies.
Bearing thrust loads are sometimes measured using strain gages secured to races of the bearing assemblies. For example, the strain gages are sometimes calibrated in a laboratory and thereafter installed in the bearing races. At least some known bearing races may need to be reworked so that the gages can be securely engaged to the races. However, reworking bearing surfaces and calibrating each strain gage may be time consuming and difficult.
At least some known strain gage configurations for measuring bearing thrust loads include leadout wires that are routed through static structures of the gas turbine engine to a power source and measurement circuit. If the wires are incorrectly connected to the measurement circuit, the thrust readings can be reversed, i.e., the thrust load may be indicated as being in a direction opposite the direction of the actual thrust load. Also, with the above described strain gage configuration, the leadout wires secured to the internal engine surfaces may work loose or fracture due to fatigue over time, possibly resulting in a loss of signal.
In addition, the strain gage readout may be dependent upon temperature correction. To compensate for temperature affects on the gages, it may be necessary to mount temperature sensors in the region of the strain gages, which may add complexity to the installation and measurement.
Monitoring the health of a thrust bearing in real-time is a demonstrated means for predicting bearing failure. Preventing a bearing failure is worth millions of dollars in engine downtime.